This build yields probably the best tank possible with the current PRC options. This build can take unheard of amounts of punishment that scales with level all the way to level 40. This build, however, can also dish out a serious beating as well. I call it Shaman-Duelist-Zilla.
What this build gives you: absolutely enormous AC capable of easily breaking 100 without any armor or buffs; 16 pre-epic BAB for 4 attacks/round; intelligence bonus to AC; charisma bonus to saves; devastating critical; +4d6 damage per attack when not wearing armor (Precise Strike); an animal companion that scales with level (even non-Shaman levels); a few spells from the Shaman list; turn undead (but only progresses until level 7); ability to see invisible creatures (Spirit Sight); and it can obtain huge DR from Shifter forms.
Weak points: enemies with critical immunity will slow you down, but you are a tank so you will win eventually; no healing to speak of making this build a good candidate for equipment with regeneration; due to low wisdom, this build cannot cast 4th level Shaman spells despite qualifying for them - I wouldn't worry about it, Shaman spellcasting is garbage.
Build Name: ShaDZilla
Race: Half-Ogre
STR 20
DEX 12
CON 10
WIS 13
INT 12
CHA 11
Lvl Class
1 Shaman 1: Alertness, Tumble 2, Perform 2
2 Sha 2
3 Sha 3: Endurance, Tumble 3, Perform 3
4 Sha 4: B: Dodge, 13 DEX
5 Sha 5: Tumble 4
6 Sha 6: Weapon Finesse
7 Sha 7: Tumble 5
8 Shifter (PnP) 1: 13 INT
9 Shft 2: Mobility
10 Duelist 1
11 Duel 2
12 Duel 3: Improved Critical (Rapier), 21 STR
13 Duel 4
14 Duel 5
15 Duel 6: Power Attack
16 Duel 7: 22 STR
17 Shft 3
18 Shft 4: Cleave
19 Shft 5
20 Shft 6: 23 STR
21 Shft 7: Great Cleave
22 Shft 8
23 Shft 9
24 Shft 10: Epic Willpower, 24 STR
25 Duel 8
26 Duel 9
27 Duel 10: Overwhelming Critical (Rapier)
28 Duel 11: 25 STR
29 Duel 12
30 Duel 13: Devastating Critical (Rapier), B: Epic Reflexes
31 Duel 14
32 Duel 15: 12 CHA
33 Duel 16: Armor Skin, B: Great Dexterity
34 Duel 17
35 Duel 18
36 Duel 19: Epic Fortitude, B: Great Dexterity, 13 CHA
37 Duel 20
38 Duel 21
39 Duel 22: Great Intelligence, B: Great Dexterity
40 Duel 23: 14 CHA
Suggested forms: the biggest, baddest dragon equal to or less than your HD you can find! Or anything with a high AC and DR that can fit through doors.
Note, make sure to buy off the half-ogre level adjustment as soon as you can (level 6 and 9). For all this build's abilities to work you must 1) not wear any actual armor (clothes with an AC bonus and robes are fine), 2) wield a light piercing weapon (rapier works as you are innately large-sized), 3) not have anything in your off-hand, and 4) have fighting defensively turned on (enabling sticky combat modes is recommended).